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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang incorrectly rejects default construction of union with nontrivial member"
href="https://bugs.llvm.org/show_bug.cgi?id=49072">49072</a>
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<th>Summary</th>
<td>Clang incorrectly rejects default construction of union with nontrivial member
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++2a
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>mschellenbergercosta@googlemail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Consider the following valid TU:
```cpp
struct TriviallyConstructible {};
struct BadNontrivialClass {
BadNontrivialClass() {}
};
union U {
TriviallyConstructible first{};
BadNontrivialClass second;
};
U u;
```
Currently clang rejects this with:
```
<source>:11:3: error: call to implicitly-deleted default constructor of 'U'
U u;
^
<source>:8:24: note: default constructor of 'U' is implicitly deleted because
variant field 'second' has a non-trivial default constructor
BadNontrivialClass second;
```
However, according to the standard
(<a href="https://eel.is/c++draft/class.union#general-4">https://eel.is/c++draft/class.union#general-4</a>) the member initializer of
`first` makes this a valid construct.</pre>
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